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  1. #1
    Read, Ride, Repeat ModelT's Avatar
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    Road Bike, Mountain Gears?

    Hello fellow Clydes and Athenas:

    Me and my road bike have a very difficult time getting up hills.
    Even in the 'Granny' front 30T ring and the big 25T back cog, I have to seriously mash the pedals to move up the mountain.
    Is it possible to put a big 11-34 mountain/commuter cassette on a Trek 1500 Road Bike?

    Anybody else have a similar issue?

    Thanks

  2. #2
    Banned. Mr. Beanz's Avatar
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    I've heard of some ridrs doing it but they had to replace the rear derailleur with a mountain bike type like an LX or an XT.

    Roadie rear der's aren't able to handle taller cogs (gear rings).

  3. #3
    cycling n00b Black Shuck's Avatar
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    Shimano road derailleurs take up to 28t cogs, MTB derailleurs up to 34t, maybe more.

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    Senior Member Wogster's Avatar
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    Quote Originally Posted by ModelT View Post
    Hello fellow Clydes and Athenas:

    Me and my road bike have a very difficult time getting up hills.
    Even in the 'Granny' front 30T ring and the big 25T back cog, I have to seriously mash the pedals to move up the mountain.
    Is it possible to put a big 11-34 mountain/commuter cassette on a Trek 1500 Road Bike?

    Anybody else have a similar issue?

    Thanks
    The answer is a qualified maybe, it depends on the capacity on your rear dérailleur, what you need is a simple number, take the number of teeth on your largest chain-ring and largest gear, add them together, take the smallest chain-ring and smallest gear, add those together and subtract from the largest set, this will give you a number. You do this for the set you want, not the set you have. Now if you have Shimano components you go to the Shimano website and look up the rear dérailleur that you have, if it's capacity is more then the number you came up with, your fine, if it's smaller by say 1 or 2 your probably also okay, if more, then you will need to change the rear dérailleur for one that has a higher capacity, you will also need a new chain.

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    I have something similar. A mountain crank and 12-26 8sp in the rear. It works well for me. I almost never need the granny, but it's there if I do.

  6. #6
    Senior Member Bill Kapaun's Avatar
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    Quote Originally Posted by Wogsterca View Post
    The answer is a qualified maybe, it depends on the capacity on your rear dérailleur, what you need is a simple number, take the number of teeth on your largest chain-ring and largest gear, add them together, take the smallest chain-ring and smallest gear, add those together and subtract from the largest set, this will give you a number. You do this for the set you want, not the set you have. Now if you have Shimano components you go to the Shimano website and look up the rear dérailleur that you have, if it's capacity is more then the number you came up with, your fine, if it's smaller by say 1 or 2 your probably also okay, if more, then you will need to change the rear dérailleur for one that has a higher capacity, you will also need a new chain.
    You're describing chain wrap capacity.
    That's only 1/2 the equation. The other 1/2 is maximum cog size.
    Typical Shimano road RDER's won't handle a 34T cog. They are rated about 27-28, but will often handle a 30T.

  7. #7
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    Officially, Shimano says that rear derailleurs for road bikes max out with a 27-tooth cog. The guys over in the Mechanics forum will tell you that if you replace the "B adjustment" screw with a longer one, you can probably get away with running a larger rear cog. I have to admit that I haven't tried this myself, but it's probably the first thing I'd try if I wanted lower gearing on my road bike...

  8. #8
    Gears? CliftonGK1's Avatar
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    Quote Originally Posted by sstorkel View Post
    Officially, Shimano says that rear derailleurs for road bikes max out with a 27-tooth cog. The guys over in the Mechanics forum will tell you that if you replace the "B adjustment" screw with a longer one, you can probably get away with running a larger rear cog. I have to admit that I haven't tried this myself, but it's probably the first thing I'd try if I wanted lower gearing on my road bike...
    I wouldn't try a 34t, but I managed to shoehorn an 11-32t PG-970 cassette on my Tiagra mid-cage RD. I'm running the stock Tiagra der's on my Cross Check, swapped out that cassette and the inner chainring (with a 34t) so I have a 34/32 combo on the low end. Not exactly mountain or touring gears, but it gets me and my groceries up and down the hills.

  9. #9
    Read, Ride, Repeat ModelT's Avatar
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    Experimental results:

    I mounted an 8 speed mountain wheel with a 13-32 cassette on the bike to see what would happen.
    (No riding here, just slow, no-load spinning to see what the rear derailleur would do)

    It did actually shift up to the 32 cog, but made a lot of noise. I might try CliftonGK1's advice and try an 11-32 nine speed and see how much clearance the B screw can provide.

    "I know just enough to be dangerous"

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    I am no mechanic, but what about changing the the cassette in addition to the front chain ring to something similar to a mtb set up but still maintain the roadie components.
    We cannot solve problems with the same level of consciousness that created them. A.E.

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  11. #11
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    I replaced my b-tension screw with a longerone years ago and it worked well. I had several derailleurs ripped from my bike by stumps or sticks and the only replacement I could get was an old road derailleur. I used a long screw, bent it to hit the stop on the hanger and had my friend weld it in place. It worked great.

    If I had to do the same thing today I would not, though. I would just go and buy a Deore derailleur. THey are cheap and they work well.

  12. #12
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    When we built up my bike, the only crank we had available was from a old mtb, so I've been running that with a regular road cassette on the rear all summer. There have been times I've really enjoyed that ultra granny gear.
    Well, Yeah. Because that's what cake is FOR.

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    Quote Originally Posted by cohophysh View Post
    I am no mechanic, but what about changing the the cassette in addition to the front chain ring to something similar to a mtb set up but still maintain the roadie components.
    The problem is one of compatibility. As mentioned previously, most rear derailleurs designed for road bikes can't handle the large cogs on a MTB cassette. There's a similar problem with front derailleurs. I forget the exact numbers but I think a triple FD for a road bike can only handle a difference of 22 teeth between the small chain ring and the large. For a double FD, I think it's... 16 teeth?

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    I have a Specialized Tricross, the Rear Cassette is a Shimano 9spd 11-34t... however it utilizes a MTB Shimano Deore LX Rear Derailleur (Long Cage). The Crank is a triple chainring 50x39x30T set, with a Tiagra Front Derailleur.

    The Tricross is a Road bike built for off-road riding (cyclocross), so I have no doubt that you can put mountain gearing on a road bike... you just might have to replace some additional parts to get it to work properly.

  15. #15
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    Salsa makes a 26T granny chainring that could be of significant help, but you have to shift down to it with a little finesse. If that isn't enough, do the mountain cassette and rear derailleur as well. You may well be able to ride up a vertical wall with that combination.

  16. #16
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    This is one area where my MTB commuter shines. I hit a bunch of hills, and I never run out of gears-normally stay in 2-3 2-4 for extended climbs, but it is nice to know that the small ring is there if I ever need it.

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    Quote Originally Posted by ssridinyob View Post
    Salsa makes a 26T granny chainring that could be of significant help, but you have to shift down to it with a little finesse. If that isn't enough, do the mountain cassette and rear derailleur as well. You may well be able to ride up a vertical wall with that combination.
    Remember that the front derailleur places limits on what chain rings you can use. In the case of Shimano, most double chain ring FDs only support a 16-tooth difference between the smallest chain ring and the largest. A triple chain ring FD will support a 22-tooth difference. Which means that if you opt for the 26-tooth chain ring, your max is limited to either 42 or 48 teeth. My guess is that if you need a 26-tooth chain ring to get up a hill, you're going to want a large chain ring with more than 48 teeth on the descent...

  18. #18
    Senior Member DieselDan's Avatar
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    Easy done with a Shimano Deore, XT, or XTR rear derailer, as the pull ratio is the same. Couple that with a 28/38/50 crankset and you'll be good to go.
    Last edited by DieselDan; 07-29-08 at 08:41 AM.
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  19. #19
    Senior Member Bill Kapaun's Avatar
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    Quote Originally Posted by ModelT View Post
    Experimental results:

    I mounted an 8 speed mountain wheel with a 13-32 cassette on the bike to see what would happen.
    (No riding here, just slow, no-load spinning to see what the rear derailleur would do)

    It did actually shift up to the 32 cog, but made a lot of noise. I might try CliftonGK1's advice and try an 11-32 nine speed and see how much clearance the B screw can provide.

    "I know just enough to be dangerous"
    Did you lengthen your chain first?
    IF the chain was properly sized for a 25T cog, it'll be about 3-4 links too short for a 32T cog.
    That can cause damage to the RDER, in addition to "noise", if you try shifting to BIG:BIG.
    Noise could be also caused by a slight difference in cassette alignment between different wheel sets, even between 2 different 9 speeds.

  20. #20
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by ssridinyob View Post
    Salsa makes a 26T granny chainring that could be of significant help, but you have to shift down to it with a little finesse. If that isn't enough, do the mountain cassette and rear derailleur as well. You may well be able to ride up a vertical wall with that combination.
    The bolt ring circle on most road cranks is capable of handling a 24 tooth ring. A cassette change may get you to a 29 or 30 tooth on the cassette without too many problems. Changing to a mountain bike rear derailer isn't hard or expensive. Jenson USA sells a Deore for $20.
    Stuart Black
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  21. #21
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by sstorkel View Post
    Remember that the front derailleur places limits on what chain rings you can use. In the case of Shimano, most double chain ring FDs only support a 16-tooth difference between the smallest chain ring and the largest. A triple chain ring FD will support a 22-tooth difference. Which means that if you opt for the 26-tooth chain ring, your max is limited to either 42 or 48 teeth. My guess is that if you need a 26-tooth chain ring to get up a hill, you're going to want a large chain ring with more than 48 teeth on the descent...
    I've run 52 outers and 24 tooth inners without problems. The front derailer will handle the difference. Shimano is waaaay conservative on their tooth differences.
    Stuart Black
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